First-principles study on adsorption of Au atom on hydroxylated SiO<Subscript>2</Subscript> surface

Adsorption of single gold (Au) atom at three kinds of sites (hollow, bridge and top) on the hydroxylated β-cristobalite SiO2 (1 1 1) surface was studied using the first-principles calculations with general gradient approximation (GGA). The results of adsorption energies and density of electronic states (DOS) suggest that the hollow and bridge sites have the basically equal capability of binding Au, while the ability of the Top site is weaker. Two new energy levels emerge after the adsorption at all sites; i...     

Cu（111）-c（2×2）-Cl吸附结构第一性原理研究

密度泛函理论（DFT）总能计算研究了1／2ML覆盖度下氯原子在Cu（111）表面的吸附结构。计算结果表明：在Cu（111）-c（2×2）-Cl吸附结构中两个不同的Cl原子分别吸附于Cu（111）表面的fcc谷位和hcp谷位,每个氯原子的平均吸附能为2．631eV,氯原子的平均吸附高度ZCl-Cu。为0．209nm。Cu（111）-c（2×2）-Cl表面的功函数为5．778eV。     

氢原子在Cu，Pt（100），（111），（110）面上的吸附扩散势能面结构的研究

构成了Ｈ－ＣＵ，Ｈ－Ｐｔ相互作用的５参数Ｍｏｒｓｅ势，用经典的对势方法研究了氢原子在Ｃｕ（１００），ＣＵ（１１１），ＣＵ（１１０），Ｐｔ（１００），Ｐｔ（１１１），Ｐｔ（１１０）面上的吸附和扩散，得到了氢原子在６个表面上的吸附位、吸附几何、键能及本征振动等数据和实验结果附和得很好。同时系统地研究了６个体系的吸附扩散势能面结构。此外，还重点研究了氢原子在ＣＵ（１００）、Ｐｔ（１１１）两体系的吸附态之间经过渡态扩散的活化能，扩散系数及隧道效应对扩散系数的影响，这些工作都基本上达到预期的结果，证实了所采用的方法的可行性。     

Study on H atoms diffusion and adsorption properties of MgH<Subscript>2</Subscript>-V systems

Based on experimental results that VH_0.81/MgH₂ interface was found during the process of mechanically milling MgH₂+5at.%V nanocomposite, H atoms diffusion and adsorption properties of MgH₂-V systems have been investigated by using a first-principles plane-wave pseudopotential method based on the density functional theory. The results are as follows. When VH/MgH₂ interface is formed due to V alloying MgH₂ phase, the vacancy formed by H atoms near VH phase region is more stable than that without V alloying, while vacancy near MgH₂ phase region is less stable than that without V alloying. During the process of H atoms diffusion after V alloying, the max migration barrier energy of H atoms in MgH₂-V systems is reduced compared with that of MgH₂ phase, which means that H atoms diffuse easily. When H diffuses into VH from MgH₂ across VH/MgH₂ interface, among three substitutions such as the replacement of H for V vacancy, or interstitial site or V atoms, the replacement of H for V vacancy has the strongest diffusion ability, next interstitial site, and finally V atoms site. As far as H adsorbed on different surfaces of VH phase is concerned, physical adsorption is carried out more easily than chemical adsorption, and the behavior of H atoms adsorbed on the surface near VH phase region can be found more easily than that near MgH₂ phase region. Supported by the Ministry of Science and Technology of China (Grant No. 2006CB605104) and the National Natural Science Foundation of China (Grant No. 50771044)     

Cu(100)表面空位扩散的分子动力学研究

采用原子镶嵌(EAM)势,利用分子动力学方法研究了单个空位在C u(100)表面及其附近区域扩散分子动力学过程,给出了空位在此表面附近不同层的形成能和迁移能。研究结果表明空位在表面形成能最小,随着层数增加空位形成能也增加,直到表面以下第五层达到体值。对于空位迁移,计算结果表明处于表面层附近的空位容易向上一层迁移直至迁移到表面。     

H原子在Au_xAg_(1-x)表面上的化学吸附

采用相干势近似（CPA）和Einstein-Schrieffer化学吸附理论计算了H原子在AuxAg1-x合金表面上的化学吸附能．计算结果表明，化学吸附能△E随着Au体浓度Xb的增加而减小；Ag在清洁合金表面的偏析导致化学吸附能△E增加；化学吸附诱导表面偏析的影响在化学吸附中不能被忽略，化学吸附能随H原子覆盖度θ的增大而减小．     

氢分子在Cu (111) 表面吸附与解离的第一性原理研究

采用基于密度泛函理论的第一性原理对氢分子与Cu (111) 表面的相互作用进行了研究。计算结果表明氢分子是否解离取决于氢分子距表面的初始距离和其初始构型。当氢分子垂直于Cu (111) 表面放置时,在距离表面0.37~4.0 ?范围内,氢分子与Cu (111) 表面相互作用后均不会解离,物理吸附在Cu (111) 表面;当氢分子平行于Cu (111) 表面放置时,有的氢分子解离成氢原子后化学吸附于表面六角 (hcp) 或面心 (fcc) 位。氢分子在桥位 (bri) 并沿[211]方向平行靠近Cu (111) 表面时,氢分子解离的临界距离约为1.35 ?,其他情况下在0.65~0.85 ?之间。     

CO在Cu表面吸附过程中电荷转移的理论研究

应用密度泛函理论,对CO分子在Cu(100)表面的吸附过程进行了研究。计算了CO分子以垂直方式在3种不同吸附位置吸附时CO分子和Cu(100)表面原子的电荷分布。结果表明:与碳原子最近邻的铜原子表面上发生明显电荷转移,而其他表面原子及体相原子的电子结构没有变化。Mulliken集居数及局域态密度分析表明,吸附过程中CO分子与表面Cu原子相互作用主要是CO分子内杂化轨道和3d,4s,4p(Cu)的贡献。     

Pore structure of SWNTs with high hydrogen storage capacity

This paper reveals, by analyses of nitrogen cryo-adsorption isotherm, the energetic and structural heterogeneity of single-walled carbon nanotubes (SWNTs) which has a high hydrogen storage capacity. It was found that SWNTs had manifold pore structures and distributed surface energy. By comparison of the pore structures and energy distributions of SWNTs before and after hydrogen adsorption, it is preliminarily indicated that hydrogen adsorption occurred in micropores and mesopores with smaller diameter, and that the pores of different diameters determined different hydrogen adsorption processes and underwent different structure changes during hydrogen adsorption.     

Electronic structures and properties of Ti, Zr and Hf metals

Ａｔｒｏｏｍｔｅｍｐｅｒａｔｕｒｅａｎｄａｍｂｉｅｎｔｐｒｅｓｓｕｒｅ ,ｔｈｅｓｔａｂｌｅｃｒｙｓｔａｌｌｉｎｅｓｔａｔｅｏｆｔｈｅｅａｒｌｙｔｒａｎｓｉｔｉｏｎｍｅｔａｌｓＴｉ,ＺｒａｎｄＨｆｉｓａｈｅｘａｇｏｎａｌｃｌｏｓｅ ｐａｃｋｅｄ(ｈｃｐ)ｓｔｒｕｃｔｕｒｅ (αｐｈａｓｅ) .Ａｔｈｉｇｈｔｅｍｐｅｒａｔｕｒｅ ,ａｌｌｔｈｅｓｅｔｈｒｅｅｍｅｔａｌｓｕｎｄｅｒｇｏａｐｈａｓｅｔｒａｎｓｆｏｒｍａ ｔｉｏｎｉｎｔｏａｂｏｄｙ ｃｅｎｔｅｒｅｄｃｕｂｉｃ (ｂｃｃ)ｓｔｒｕｃｔｕｒｅ (βｐｈａｓｅ) …     

Electronic structures and properties of V, Nb and Ta metals

0　ＩｎｔｒｏｄｕｃｔｉｏｎＴｏｄｅｓｉｇｎａｌｌｏｙｓｓｃｉｅｎｔｉｆｉｃａｌｌｙ ,ｓｙｓｔｅｍａｔｉｃｓｃｉｅｎｃｅｆｒａｍｅｏｆｍｅｔａｌｓａｎｄａｌｌｏｙｓｉｎｃｌｕｄｉｎｇｔｈｅｓｙｓｔｅｍａｔｉｃｓｃｉｅｎｃｅｏｆｐｕｒｅｍｅｔａｌｓ (ｏｎｅ ａｔｏｍ (ＯＡ)ｔｈｅｏｒｙ) [1,2 ]ａｎｄｔｈｅｓｙｓ ｔｅｍａｔｉｃｓｃｉｅｎｃｅｏｆａｌｌｏｙｓ (ｃｈａｒａｃｔｅｒｉｓｔｉｃｃｒｙｓｔａｌ(ＣＣ)ｔｈｅ ｏｒｙ) [3～ 6 ]ａｒｅｅｓｔａｂｌｉｓｈｅｄ ,ｗｈｉｃｈｃａｎｇｉｖｅｄｉａｇｒａｍｓｏｆ…     

空位和B、N、Al、P掺杂对Li在石墨烯上吸附的影响

采用基于密度泛函理论的第一性原理计算了空位和B、N、Al、P掺杂对Li在石墨烯上吸附的影响,结果表明:Li原子在完整石墨烯上吸附的稳定位置为心位,吸附高度在覆盖度低于1/40 ML时趋于恒值;B、N、P原子掺杂比Al掺杂石墨烯容易;杂质类型对Li在石墨烯上的吸附位置有显著的影响;空位和B、Al、P替位掺杂均加强了Li在石墨烯上的吸附,Al替位掺杂对Li在石墨烯上吸附的影响相对较大;Al、P掺杂改变了Li的稳定吸附位置(由心位移到顶位);Li在空位缺陷和N掺杂石墨烯上吸附后,两体系具有磁性,Li吸附在B-graphene、Al-graphene、P-graphene体系磁矩为零,不显示磁性。     

Interface structure of Ag (111)/SnO<Subscript>2</Subscript> (200) composite material studied by density functional theory

Electric contact material of Ag/SnO₂ was successfully synthesized by in situ process method. The interface structure was characterized by high-resolution transmission electron microscopy (HTEM) and simulated at atomic scale on computer. The mean-square displacements of atoms near the interface were calculated, and the results showed that near the interface both Ag side and SnO₂ were mismatched and this effect decays rapidly far from the interface. By inspecting the calculated density of states (DOS), we found that the electric-conductivity of this composite material was decreased because of the localized 4d and 2p electrons of Ag and O near the Fermi surface, respectively. Electron density changed acutely across the interface, so that there was no extra compound precipitated. A micro-electric field also formed in the whole material due to the interface structure, and this may affect the electron conduction and the related electric-conductivity of the composite. It is found that the interface cohesive energy of Ag (111)/SnO₂ (200) was −3.50 J/m², which is higher than the experimental results. Supported by the National Natural Science Foundation of China (Grant No. 2008CB617609), the Natural Science Foundation of Yunnan Province (Grant No. 2006E003Z) and Science Innovation Foundation of Kunming University of Science and Technology     

Study on Lubricant Materials Transfer between Head and Disk

润滑材料在磁头磁盘间转移特性的研究

曾秦阳,敖宏瑞*,姜洪源*

（哈尔滨工业大学机电学院,哈尔滨 150001）

中文说明：

近年来,随着硬盘存储密度的增加,磁头滑块的飞行高度逐渐降低,这使得润滑材料更容易在磁头与磁盘之间转移。润滑材料的转移能力不仅与硬盘的工作条件有关,还与润滑材料（全氟聚醚—PFPE）自身特性和磁盘的类金刚石（DLC）涂层有关。本文基于分子动力学原理,建立了几种常见的润滑材料分子与磁盘的吸附模型以及在空气中的扩散模型并进一步仿真计算了对应的吸附能和扩散系数。研究表明,润滑材料的分子量、分子结构和端基官能团以及磁盘的含碳量对润滑材料的转移能力均有影响,后两个因素对转移能力的影响较大。

关键字：分子动力学;吸附能;扩散系数

     

酚醛-乙醇体系在石英纤维表面吸附行为研究

采用漫反射红外光谱研究酚醛树脂-乙醇体系在石英纤维表面的竞争性吸附行为;紫外吸收光谱分析表明酚醛树脂和乙醇之间存在很强的相互作用;粘度和表面自由能测量证实作为溶剂的乙醇被优先吸附.酚醛树脂在纤维表面的吸附是溶质、溶剂和纤维表面3者之间氢键共同作用的结果,乙醇和酚醛树脂在纤维表面形成竞争性吸附,溶质-溶剂间的氢键作用不利于酚醛树脂吸附.热失重分析表明作为溶剂的乙醇被优先吸附导致树脂在一维复合材料液体成型工艺模型内部不同位置分布不均.     

煤吸附水的微观机理

根据煤大分子和表面的结构特点，应用分子热力学和表面物理化学理论分析了煤表面自由能的特征和煤吸附水的微观机理．结果表明，煤对水分子的吸收从微观上看是由于水分子与煤表面相互吸引作用的结果，这些作用力包括分子间力和氢键．煤对水分子的吸附是多层吸附，吸附第一层水主要是由于煤对水分子的氢键作用占主要地位，对其余水分子层的吸附主要是由于分子间力引起的长程力作用的结果．对水分子与煤表面的分子间力进行了估算，结果是分子间力中色散作用力占主要地位．讨论了添加活性剂润湿煤体的作用，认为这是从微观上改变了水分子与煤表面的吸引作用力的结果．研究煤吸附水的微观机理为现场优化提高煤层润湿性措施奠定了理论基础．     

特征时间规律的扩散反应理论

提出了多孔气敏薄膜电导响应扩散反应模型；通过求解和无量纲分析扩散反应方程给出了τs和τc的规律，τc=τs/r=(2/π)2kCr-10l2/D；通过理论与实验相结合的方法研究表面吸附指数γ和吸附能Ea. 实验结果表明：C2H5OH在ZnO薄膜材料上的吸附特性有下面的特点：①有两个不同温区，高于380?℃和低于380?℃的物理吸附能不同；②物理吸附能较大. 关键词：扩散反应；无量纲分析；吸附指数     

Oxygen adsorption on pyrite （100） surface by density functional theory

Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studiedby using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe^2 and S^2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.     

Calculation of electron structure by density function theory and electrochemical process of surface （100） of FeS2

The electron structure of FeS2 surface (100) was computed by DFT (density function theory) and the process of electron transfer in sulfide flotation was simulated through ab-initio calculation. The results show that the interaction between xanthate and FeS2 is controlled by the energy of valence band. The products and degree of the reaction depend on the density of state of valence band and concentration of positive hole in valence band. Interaction between xanthate and pyrite can be changed by modifying the election structure of the surface of pyrite. Xanthate is adsorbed on the surface of intrinsic pyrite. But the amount of xanthate adsorbed on the surface of the pyrite with sulfur vacancy is more than that on the surface of the intrinsic pyrite due to the higher electron and vacancy density. Xanthate is not adsorbed on the surface of pyrite with Fe vacancy because of its high Fermi energy.     

Nucleation barrier of fcc(γ)→hcp(ε) martensitic transformation in Fe-based alloys

Based on the dislocation theory and Olson's stacking fault model, a model describing the nucleation of an hcp(ε) martensite embryo at low-angle grain boundary is proposed with the influence of external stress field taken into account. The dependences of temperature (T), shear stress (τ) and dislocation density at grain boundary on the martensite nucleation in FeMnSi based alloy, as an example, are numerically simulated. It has been shown that there exist the subcritical and critical embryos during the course of ε-phase nucleation. The free energy difference between them is just the energy barrier of embryo growth. Depending on T and τ, the characteristic embryo sizes may vary in wide ranges and decrease with increasing a and decreasing T. The energy condition of martensitic transformation at Ms and critical shear stress (τc) is discussed from the viewpoint of kinetics and thus the TEM observed result that stacking fault energy is not zero at Ms temperature is reasonably explained. Besides, it is pr